As is known, many food products, such as fruit juice, pasteurized or UHT (ultra-high-temperature treated) milk, wine, tomato sauce, etc., are sold in packages made of sterilized packaging material.
A typical example of this type of package is the parallelepiped-shaped package for liquid or pourable food products known as Tetra Brik Aseptic (registered trademark), which is made by folding and sealing laminated strip packaging material.
The packaging material has a multilayer structure substantially comprising a base layer for stiffness and strength, which may comprise a layer of fibrous material, e.g. paper, or of mineral-filled polypropylene material; and a number of layers of heat-seal plastic material, e.g. polyethylene film, covering both sides of the base layer.
In the case of aseptic packages for long-storage products, such as UHT milk, the packaging material also comprises a layer of gas- and light-barrier material, e.g. aluminium foil or ethyl vinyl alcohol (EVOH), which is superimposed on a layer of heat-seal plastic material, and is in turn covered with another layer of heat-seal plastic material forming the inner face of the package eventually contacting the food product.
As is known, packages of this sort are produced on fully automatic packaging machines, on which a continuous tube is formed from the web-fed packaging material; the web of packaging material is sterilized on the packaging machine, e.g. by applying a chemical sterilizing agent, such as a hydrogen peroxide solution, which, once sterilization is completed, is removed from the surfaces of the packaging material, e.g. evaporated by heating; the web of packaging material so sterilized is maintained in a closed, sterile environment, and is folded and sealed longitudinally to form a vertical tube.
The tube is filled continuously downwards with the sterilized or sterile-processed food product, and is sealed and then cut along equally spaced cross sections to form pillow packs, which are then fed to a folding unit to form the finished, e.g. substantially parallelepiped-shaped packages.
Alternatively, the packaging material may be cut into blanks, which are formed into packages on forming spindles, and the packages are filled with the food product and sealed. One example of this type of package is the so-called “gable-top” package known by the trade name Tetra Rex (registered trademark).
The so obtained packages are conveyed from the packaging machine to further stations, in which, for instance, such packages are provided with opening or drinking features, such as opening devices, straws, etc., and/or in which they are grouped and shrink-wrapped, so as to form multi-packs adapted to be stacked in a number of horizontal layers on respective pallets destined to the retail outlets.
During the transfer from one processing station to the others, it may be necessary to stop the packages or the multi-packs at certain points of the relative conveying lines. This may occur, for instance, where two conveying lines converge in one downstream line: in this case, the packages or multi-packs arriving on one of the converging lines have to be stopped to avoid collision with the packages or multi-packs arriving at the same time on the other line.
Alternatively, it may be necessary to stop the packages or multi-packs along a relative conveying line when a breakdown occurs in the downstream processing station or even when a batch of such packages or multi-packs has to be separated from the others in the row.
In all these cases, the stopping action is performed by braking units, which are typically formed by a pair of belts arranged on both sides of the conveyor for advancing the packages or multi-packs; each belt moves along a relative closed loop comprising a work portion, cooperating with the packages or multi-packs advanced on the relative conveyor, and a return portion.
The belts can be selectively stopped to brake the row of packages or multi-packs moved by the conveyor; the force applied by the belts onto the packages or multi-packs is quite relevant as it is normally designed to withstand the thrust exerted by a great deal of items in the row.
Such relevant force may, under particular circumstances and especially when the row is formed by a reduced number of packages or multi-packs, damage the latter and/or cause the detachment of the straws.
Moreover, the relevant force applied by the belts may hurt the user in the event that the latter puts his fingers or other parts of his body between the belts and the row of packages or multi-packs; for this reason, it is normally required to arrange protective panels or devices around the area in which the belts perform their action.
Finally, it should also be observed that, when the number of packages or multi-packs in the row exceeds a certain predetermined value, the belts may loose their effectiveness.
In the light of the above, a need is felt within the industry to provide a braking unit, which is effective in stopping any number of packages or multi-packs in a row without damaging them.
A need is also felt within the industry to provide a braking unit, which is effective in stopping any number of packages or multi-packs in a row and which is safe for the user so as to not require any protection device around the working area.